#! /bin/bash
cat /var/log/auth.log|awk '/Failed/{print $(NF-3)}'|sort|uniq -c|awk '{print $2"="$1;}' > /root/black.txt
DEFINE="20"
for i in `cat  /root/black.txt`
do
        IP=`echo $i |awk -F= '{print $1}'`
        NUM=`echo $i|awk -F= '{print $2}'`
        if [ $NUM -gt $DEFINE ];
        then
         grep $IP /etc/hosts.deny > /dev/null
          if [ $? -gt 0 ];
          then
          echo "sshd:$IP" >> /etc/hosts.deny
          fi
		fi
done
rm -f /root/black.txt